How to Run a Flashlight Inspection for Cockroaches

Why this matters

Most cockroach callbacks were decided in the first ten minutes of the first visit, when the tech walked in, saw a couple of insects by the sink, and started treating the whole kitchen. Product went everywhere the cockroaches were not, and the harborage behind the dishwasher or inside the hollow cabinet base never saw any. An inspection is the job that tells you where the population lives, which species it is, and how big a problem you have. Its output is a harborage map drawn before any product leaves the bag. Everything the program does afterwards, bait, monitors, sanitation, follow-up, is placed off that map.

What to bring and how to set the room

• A bright, narrow-beam flashlight plus a spare. A wide floodlight washes out droppings in a crack; a tight beam laid flat across a surface makes them cast shadows.
• An inspection mirror on a handle, for the backs of hinges, the underside of the sink lip and behind the dishwasher.
• A flat blade or putty knife to scrape a speck and see whether it smears (fecal) or is dirt.
• A screwdriver set for kick plates and refrigerator grilles.
• Gloves, because you will put your hands under sinks and into debris. Droppings and cast skins are allergens.
• A clipboard or the tablet sketch to mark findings as you go.

Turn the lights off or low before you start, and open nothing yet. German cockroaches are strongly negative to light and run for cracks the moment a room lights up. Entering a dark kitchen, standing still, and then putting the beam on the counter edges and the sink back will show you where they run, which is the harborage. Once you have opened every cabinet and banged a few doors, that information is gone.

No product comes out during the inspection. That includes a flushing aerosol. A flushing agent is a pesticide application under its own label, it scatters insects into new cracks, and it destroys the picture you are trying to draw. If the program calls for one later, it is a treatment decision made off the map.

The route, in order

The order matters because each stop is easier to read before the next one disturbs it, and because it runs from the most likely harborage to the least. In a kitchen:

1. Stand and look, lights off then beam on. Thirty seconds. Note where anything runs.

2. Sink base. Open the door slowly and put the beam into the back corners and along the pipe penetrations through the back panel. This is the warmest, wettest, most cluttered void in most kitchens. Check under the sink lip with the mirror. Note any leak.

3. Cabinet hinges and door edges. For each base and wall cabinet near the sink, range and refrigerator, put the beam into the hinge gap from above and below. Droppings at a hinge read as a dark line of specks along the face frame.

4. Appliance voids. Remove the dishwasher kick plate and look inside at the frame edges, staying clear of the wiring junction box. Pull the refrigerator grille and look at the motor compartment frame without touching the fan or wiring. Look under and behind the range with the beam laid flat along the floor; do not pull a gas range out to look, because the flexible connector is not yours to strain.

5. Electrical boxes and plate edges. Check the edges of switch and outlet plates on the backsplash and near the appliances for specks and smear. Do not remove the plates or put anything into a box. Evidence here goes on the sketch as a finding; any work at an electrical box is a later decision made with the circuit off and proved dead.

6. Clutter and stored items. Grocery bags, cardboard flats, the appliance boxes on top of the refrigerator, the junk drawer. Cardboard corrugations are harborage, and they arrive from the store already infested.

7. Then the bathroom, in the same order: vanity base and its pipe penetrations, behind the toilet tank, the gap behind the medicine cabinet, and under the edge of the tub surround.

At each stop you are looking for the same four things. For what other evidence looks like (rodent sign, frass, damage), see 'Pest Activity Signs Reference'.

The four signs and what each one tells you

Live insects. Count them roughly and note size. Many small nymphs together means you are at or very near a harborage, because young nymphs stay close to where they hatched.

Droppings. German cockroach droppings are tiny dark specks like ground pepper, and on vertical surfaces and at harborage entrances they build into smears and stains. A dense smear at a crack mouth is an established harborage. Scrape one with the blade: fecal specks smear brown, dirt crumbles.

Egg cases (oothecae). A German female carries her egg case until it is close to hatching, so empty hatched cases end up in the harborage itself. Finding several empty cases in a crack says that crack has been producing for a while.

Cast skins. Pale, papery molts left by nymphs. They accumulate where nymphs live, so like egg cases they mark harborage rather than travel routes.

Live adults without the rest (no droppings, no nymphs, no skins) usually mean wanderers or a newly introduced population, not a nest at that spot.

German or something else

The program is different for German cockroaches than for the larger outdoor species that wander in, so make the call during the inspection, from the signs as well as the insects. Detailed identification is in 'Cockroach Species Identification - Beyond German'; at the inspection level:

• German pattern: small insects, nymphs present, pepper-fine droppings and smears in tight warm cracks in kitchens and baths, upper as well as lower cabinets. Year-round indoors. This is an indoor breeding population.
• Peridomestic pattern (American, smoky brown, oriental and others): large adults, few or no nymphs indoors, larger droppings (American droppings are cylindrical and visibly ridged), found low and near entry points: floor drains, basement, crawl access, garage door, door thresholds. Often seasonal. This is an exclusion and exterior problem as much as an interior one.

A kitchen can have both. Write them separately.

Worked example: a condo kitchen and hall bath

The call. A second-floor condo, two weeks of sightings at night on the counter by the sink. The owner has used a store aerosol twice under the sink.

What you saw, by stop.

• Stand and look. With the beam on, three small nymphs run from the backsplash behind the faucet down behind the sink cabinet's back panel.
• Sink base. Heavy pepper droppings and brown smears along the drain penetration through the back panel, two empty egg cases wedged in the gap, a slow drip at the trap slip nut and a soaked cardboard pad on the cabinet floor. Live nymphs in the gap when the beam hits it.
• Hinges. The base cabinet left of the sink: droppings at both hinges. Right of the sink (dishwasher side): nothing. Wall cabinet above the sink: a light line at the lower hinge.
• Appliance voids. Behind the dishwasher kick plate: cast skins and droppings on the left frame edge, the side against the sink base. Refrigerator motor compartment: clean. Range: clean along the floor line.
• Plate edges. The outlet beside the sink: a few specks at the plate's lower edge.
• Clutter. A stack of flattened delivery boxes beside the refrigerator: droppings in the corrugations of the bottom two.
• Bathroom. Vanity base clean, behind the toilet clean, tub edge clean.

The map. Marked as you went:

 HARBORAGE SKETCH, UNIT 2B
        wall cab  [L] light, lower hinge
 +--------+----------+--------+---------+------+
 | BASE L | SINK BASE| DISH-  | RANGE   | REF  |
 | [M] 2  | [H] drain| WASHER | clean   | clean|
 | hinges | penetr., | [M] L  |         |      |
 |        | 2 eggcase| frame  |         | [M]  |
 |        | leak     | edge   |         | box  |
 |        | [O] plate| skins  |         | stack|
 +--------+----------+--------+---------+------+
 H heavy  M moderate  L light  O outlet edge
 BATH: vanity, toilet, tub edge all clean
 Species: German, nymphs present

Reading it. Every positive finding except the box stack sits within one cabinet width of the sink base, and the sink base carries all four signs at once: live nymphs, heavy smears, egg cases and a moisture source. That is the primary harborage. The dishwasher frame and the base cabinet hinges are spread from it. The box stack is a second, separate harborage that also explains how the population may have arrived. The bathroom being clean says this is still a one-room problem. The aerosol residue under the sink is a fact the bait plan has to deal with.

What goes to the customer before any product, written up per 'Moisture and Conducive Condition Report': the leak at the trap is a plumbing repair (theirs, or their plumber's), the cardboard pad and the box stack go out today, and the aerosol stops. Then the treatment plan is built off the map, starting at the sink base, inside the program described in 'German Cockroach IPM'. Placement is in 'How to Place Gel Bait in a Kitchen'.

Where inspections go wrong

Opening everything before looking. The run-to-harborage cue is gone after the first door slams.

Reading only the floor. German cockroaches use upper cabinets and the backsplash. A hinge on a wall cabinet is a real position.

Calling a nest from adults alone. Two big adults on a basement floor near a drain are a different program than ten nymphs in a hinge.

Missing the moisture. A drip under the sink is often the reason the harborage is there. If it stays, the population comes back.

The finish test

Before any product comes out, you can point at a sketch that marks every stop checked (including the ones that were clean), rates each finding, names the primary harborage and any secondary ones, names the species pattern, and lists the conducive conditions the customer has to fix. If someone asked "why did you put bait there and not there", the sketch answers it.

References

• See related: Cockroach Species Identification - Beyond German
• See related: German Cockroach IPM
• See related: How to Place Gel Bait in a Kitchen
• See related: Pest Activity Signs Reference
• See related: Moisture and Conducive Condition Report